A known flow rate converter is disclosed in the catalog of the GOULD company (Netherlands). The known device has a body with a cylindric tube disposed therein. In the tube are disposed axial channels and its two ends are connected respectively with an incoming and an outgoing diffuser. In the body are machined inner circumferential conduits connecting the external row of axial channels with pipe connections disposed on the body to which is mounted a heating element. There are some several thousand axial channels which occupy the whole section of the tube and they have an approximately triangular section. In order to carry out investigations in the entire range, a series of ten converters with different parameters and overall sizes is needed.
The disadvantages of this known converter include complicated manufacture technology and the requirement of having an entire set of separate converters with different over-all sizes in order to cover the complete range.